In the past three and one-half years, we have developed biphasic models to describe the deformational behavior of articular cartilage, validated these models in simple loading configurations, measured some ot the intrinsic matrix biomechanical properties of normal and degenerate human articular cartilage, and utilized the measured values of these properties in simple models of joint motion. In the course of this research, we have discovered many new phenomena, several of which will be studied in depth as outlined in the present proposal. We will extend these measurements of cartilage matrix properties to several different human joints and to different areas of the joint surfaces. Finally, as a logical extension of our recent measurements on the influence of the tissue's water content on its matrix properties, we will now correlate these properties with some simple routine measurements of the tissue's biochemical composition and microscopic structure. These studies will help us to develop an understanding of the interaction and breakdown of the matrix components in naturally occurring biomechanical and structural change in human cartilage throughout life. All data will be statistically analyzed to determine: (1) differences in the progression of cartilage degeneration among various joints and areas of the joint surfaces, (2) correlations between biochemical, structural and mechanical properties unique to given sites, and (3) trends in the pooled data from all sites. Using this information, we hope that the pathological changes or rates of change of human articular cartilage's material properties, biochemistry and structure can be identified and that some mechanisms responsible for the progressive failure of the human joint structure in osteoarthritis can be determined.